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Kai Ryssdal: The Internet has done crazy things to the world of retail. Far, far beyond just shopping online. There was the un-boxing craze of a couple of years ago -- countless YouTube videos of people taking their iPhone or new TV or whatever out of its box. Now there's something called "social shopping." Used to be when you were excited something you'd bought, you'd tell your friends. In person.

The new new thing, apparently, is to share your purchases virtually, as in online. Websites are popping up all over. And other shoppers aren't the only ones paying attention.

Sally Herships reports.

Sally Herships: Have you seen the new social shopping sites, like Blippy or Swipely.com? They're like Facebook for people who are really into shopping. I wanted to check them out, so I joined Swipely.

Sound of typing

Herships: OK, sign up now...

The sites let you see what other people buy, and sometimes where they bought it and what it cost. When I logged in, I saw pictures from Angus Davis, Swipely's founder. He bought some nautically-themed pillows for his guest room. Another Swipely employee seems to be a big fan of Starbucks.

Herships: Wow, he buys a lot of coffee.

Here's how it works: You give your e-mail account or your credit card number to the website. Then, when you buy something online and get e-mailed a receipt, or use your credit card, your purchase gets posted to your profile.

Herships: I am actually going to post my purchase of a toner cartridge for my laser printer.

Yeah, I'm not really a big shopper; we are in the middle of a recession. So I asked Rachel Lawes why people use these sites. Lawes studies consumer behavior, and says the sites look a lot like Facebook, so they're familiar. They're also fun. And, Lawes says, when you post your purchases, you feel responsible, like you're keeping better track of your money.

Rachel Lawes: Then, you can continue to spend your money on whatever the hell you like and feel good about yourself, feel morally shored up. Because tracking your spending is in itself a responsible thing to do.

But what about giving away all that personal information? In April, Blippy leaked the credit-card numbers of some of its users. Shouldn't shoppers be concerned about their privacy?

Yes, says Antony Lee. He's CEO of start-up WeShop.com, an online shopping network. Lee says consumers should be concerned -- that if they give away their privacy, they're getting something in return.

Antony Lee: I think the privacy debate is actually the wrong way around. The privacy debate shouldn't be about what is being taken. It should be about the value of what's being taken and who's entitled to that value.

Lee says WeShop will let consumers trade directly with retailers -- data for deals.

Lee: The value of a simple receipt in the hands of a competitor, for you is very valuable. Because it tells the competition, "Oh, this person is buying such and such, is buying Brand A."

Now Brand A's competitors know what kind of, say, orange juice, you like and what price you'll pay for it. They can try to steal your business by offering you a better deal.

Eric Greenleaf is a professor of marketing at NYU's Stern School of Business. He says social shopping networks could change business as usual.

Eric Greenleaf: This idea of having a common data set for all the purchases that millions of people are making is really revolutionary. The only firms who can do that right now are credit-card companies.

Greenleaf says the new data could make it easier for small businesses to target their customers. I asked him if he think the sites will catch on.

Greenleaf: Many consumers may not want people to know that they're going to the store to buy something like a laxative. But if they bought a new car or a new TV or a new camera, they're probably very happy to tell people about it.

And all that bragging about what you buy, that's what sites like Blippy and Swipely.com are counting on.

I'm Sally Herships for Marketplace.